Detectors and sensors find many applications in commercial and defense environments. In application, ultraviolet (UV) detectors have great selective sensitivity with no response for wavelengths exceeding 290 nanometers.
UV sensors offer several advantages over present infrared (IR) and radar based sensors. Unlike IR sensors, ultraviolet sensors can easily distinguish between the hot plume emitted from a rocket on lift off and the rocket itself. Further, the UV sensors are smaller, less expensive and do not require cooling during operation. UV sensors are also not overloaded by other sources of radiation such as explosions from conventional or nuclear devices.
Ultraviolet detection is also at the heart of several commercial applications. These applications include industrial and residential flame safeguards. Safety considerations require these sensors to be installed at every oil and gas power facility, as well as residential and commercial boilers and oil heaters. The development of highly sensitive UV sensors is desirable to meet the needs of these commercial and defense applications.
Two common requirements that all these application areas impose on the sensor system are high sensitivity and a high rate of rejection for IR/visible energy. The high sensitivity requirement necessitates the use of a high gain photoconductor or photocathode sensor based on a material system with a direct bandgap matching the desired detection wavelength.
The second key requirement is that of a sharp, long wavelength cutoff. While wavelength cutoff may be improved by using thin film filters, the material choices for these thin film filters are very limited for the wavelengths of interest. Organic materials presently used make the filters very fragile but also greatly reduce the peak transmission.
It is therefore highly desired to develop a sturdy, high rejection filter suitable for use in conjunction with UV sensors for a variety of applications.